It has been found that a worker at a computer workstation can be more productive and can be expected to be absent less than one who is uncomfortable. A particular problem is presented by the worker's chair which is normally adjustable two ways: the heights of the seat cushion and of the back rest can be changed and fixed at any level.
The height of the backrest is quickly established by the worker for lower-back support. Normally this adjustment can be made easily, since a too high or too low backrest is clearly uncomfortable.
The seat height is, however, quite a bit harder to establish. The best seat height has been determined by the science of ergonomics to be a function of the length of a person's lower leg, including any shoe worn. The seat height must be a predetermined distance below the axis of the knee joint so that the upper legs can be fairly level, the lower legs vertical, and both feet flat on the floor. This position has been found to be the least stressful for the person in the chair and encourages proper posture so that fatigue is minimized.
Unfortunately this dimension is not normally known, like a person's height, and requires a yardstick or the like to determine. Even taking this measurement is not something one can do oneself, and it in fact requires a trained person to ascertain the correct chair height. Once the ideal chair height is determined, the measuring tool must be employed again to set the chair.